(Personal Note: This was delayed due to my vacation.)
Note: To help refresh your memory, wiki links are provided for characters when available.
Michael Mosley guest starred as 'Malcolm,' the artist living in Dave & Max's crawlspace. Previously, he played the role of 'Drew,' on the final season of Scrubs. Coincidentally, his character on Scrubs was the boyfriend of 'Denise,' played by Eliza Coupe who is 'Jane' in this series.
Michael Clarke Duncan guest starred as 'Leo,' Walter's "legal advisor." Although he is well known from a variety of projects, he's probably best known for his role as 'John Coffey' in Stephen King's The Green Mile.
Danny Trejo guest starred as 'Bishop Edward Galano,' the expert on Vatican treasure ships. He's very recognizable from Quentin Tarantino and Robert Rodriguez projects, and he was recently the star of the movie Machete.